In order to incorporate infrared colloidal nanocrystal quantum dots into silicon matrix to develop silicon-based light emitters, we report in this paper the epitaxial growth of PbS shells over PbSe NQDs with monolayer precision. The core-shell infrared NQDs were ligand-exchanged with short-chain alkyl amine molecules, and the photoluminescence (PL) efficiency of the surface-engineered core-shell nanoparticles was substantially higher than that of the plain core structures undergoing the same surface processing, which reveals less ligand-dependence and enhanced chemical robustness in the core-shell NQDs. The wider band-gap (Zn,Cd)S shells effectively passivate and protect the radiative CdSe cores during the “ligand exchange” process, which might eventually lead to efficient emissions from the NQD-silicon heterojunctions.